Youth with externalizing psychopathologies, including attention-deficit/hyperactivity disorder, oppositional defiant disorder, and conduct disorder, present with diverse kinds of impulsivity symptoms, which in turn reflect deficits in regulatory control functioning. An emerging neurodevelopmental model, which we call the Impulsivity as Immaturity Model, could potentially transform our understanding of the brain basis of regulatory dysfunction. The brain's regulatory control architecture (RCA) undergoes massive maturation during childhood and adolescence. The Impulsivity as Immaturity Model proposes that aberrant maturation in distinct components of the RCA gives rise to distinct patterns of impulsivity symptoms-e.g., delayed maturation in certain attention control components gives rise to attentional variability, a specific form of attention dysfunction. Informed by this model, we will use a mixed cohort/longitudinal design enrolling 135 healthy youth and 135 youth with externalizing psychopathologies. Using advanced multivariate/multimodal analytic methods, we will map the normative neurodevelopmental trajectories of major components of the RCA including components involved in attention, motor, emotion, and appetitive control. We will then construct multivariate models that predict different forms of impulsivity based on neurodevelopment patterns of RCA components. Successful completion of this project will be a critical first step in development of a new class of imaging-based immaturity biomarkers that index distinct types of impulsivity irrespective of the specific externalizing disorders in which they manifest. This will lead to earlier, more reliable diagnosis of impulsivity problems in youth and spur the development of transdiagnostic, biologically based interventions that target specific forms of RCA dysmaturation.